A low-energy monochromated electron gun for inverse photoemission spectroscopy is designed and investigated using CST particle tracking. The system combines a prescribed electron-emission boundary, two reversed electrostatic sector monochromators, and a five-stage transfer lens. Separately optimized 127°, 144°, and 162° sectors are compared, and the 144° configuration is selected for its reported 1.361 meV energy width and complete transmission in the single-stage calculation. With two 144° sectors, the reported output widths are 4.383, 11.491, and 10.990 meV for zero, 6%, and 12% initial energy-spread settings, respectively. Under the same lens-input conditions, the five-stage lens reduces the beam extent at a plane 20 mm downstream from 4.5 mm × 4.5 mm to 1.6 mm × 1.6 mm relative to the three-stage lens, while maintaining approximately 5 eV mean output energy. The integrated model gives an approximately 0.35 mm × 0.16 mm footprint. Its energy-distribution fit is centered at 5.036 eV with a full width at half maximum of 12.3 meV. These results support the proposed combination of low-energy selection and downstream beam delivery.

low-energy electron gun, electrostatic sector monochromator, electron-optical simulation, transfer lens, inverse photoemission spectroscopy